Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D167/00—Coating compositions based on polyesters obtained by reactions forming a carboxylic ester link in the main chain; Coating compositions based on derivatives of such polymers
  • C09D167/02—Polyesters derived from dicarboxylic acids and dihydroxy compounds
  • C09D167/025—Polyesters derived from dicarboxylic acids and dihydroxy compounds containing polyether sequences
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D167/00—Coating compositions based on polyesters obtained by reactions forming a carboxylic ester link in the main chain; Coating compositions based on derivatives of such polymers
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D167/00—Coating compositions based on polyesters obtained by reactions forming a carboxylic ester link in the main chain; Coating compositions based on derivatives of such polymers
  • C09D167/02—Polyesters derived from dicarboxylic acids and dihydroxy compounds
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D5/00—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes
  • C09D5/03—Powdery paints
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/0008—Organic ingredients according to more than one of the "one dot" groups of C08K5/01 - C08K5/59
  • C08K5/0025—Crosslinking or vulcanising agents; including accelerators
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/04—Oxygen-containing compounds
  • C08K5/15—Heterocyclic compounds having oxygen in the ring
  • C08K5/151—Heterocyclic compounds having oxygen in the ring having one oxygen atom in the ring
  • C08K5/1515—Three-membered rings
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/16—Nitrogen-containing compounds
  • C08K5/20—Carboxylic acid amides
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L2205/00—Polymer mixtures characterised by other features
  • C08L2205/02—Polymer mixtures characterised by other features containing two or more polymers of the same C08L -group
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L33/00—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides or nitriles thereof; Compositions of derivatives of such polymers
  • C08L33/04—Homopolymers or copolymers of esters
  • C08L33/06—Homopolymers or copolymers of esters of esters containing only carbon, hydrogen and oxygen, which oxygen atoms are present only as part of the carboxyl radical
  • C08L33/062—Copolymers with monomers not covered by C08L33/06
  • C08L33/068—Copolymers with monomers not covered by C08L33/06 containing glycidyl groups
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L67/00—Compositions of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Compositions of derivatives of such polymers
  • C08L67/02—Polyesters derived from dicarboxylic acids and dihydroxy compounds
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L67/00—Compositions of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Compositions of derivatives of such polymers
  • C08L67/02—Polyesters derived from dicarboxylic acids and dihydroxy compounds
  • C08L67/025—Polyesters derived from dicarboxylic acids and dihydroxy compounds containing polyether sequences

Definitions

• the present invention relates to thermosetting powder coating compositions.
• the invention also relates to the use of said compositions for the preparation of powdered paints and varnishes for the making of coatings and to coatings obtained therewith.
• Thermosetting powder compositions are well known in the art and are widely used as paints and varnishes for coating the most various articles.
• the advantages of these powder coatings are numerous; on the one hand, the problems associated with solvents are completely eliminated, and on the other hand, the powders are used without any loss since only the powder in direct contact with the substrate is retained on the article, the excess powder being, in principle, entirely recoverable and reusable.
• the powder coating compositions are preferred to coating compositions in the form of solutions in organic solvents.
• thermosetting powder compositions have already been widely used in the coating of domestic electrical appliances, automobile industry accessories, and the like. They generally contain a thermosetting organic binder, fillers, pigments, catalysts and various additives used to adapt their properties to their intended use.
• thermosetting powder compositions There are various types of thermosetting powder compositions.
• the best known compositions contain either a mixture of carboxyl group-containing polymers, such as a carboxyl group-containing polyester or polyacrylate, and epoxy compounds, such as triglycidyl isocyanurate, glycidyl group-containing acrylic copolymers or ⁇ -hydroxyalkylamides or a mixture of hydroxyl group-containing polymers, most often a hydroxyl group-containing polyester, with blocked or non-blocked isocyanates, melamine resins, and the like.
• carboxyl group-containing polymers such as a carboxyl group-containing polyester or polyacrylate
• epoxy compounds such as triglycidyl isocyanurate, glycidyl group-containing acrylic copolymers or ⁇ -hydroxyalkylamides or a mixture of hydroxyl group-containing polymers, most often a hydroxyl group-containing polyester, with blocked or non-blocked isocyanates, melamine
• polyesters are usually prepared from aromatic dicarboxylic acids, mainly terephthalic acid and isophthalic acid and optionally a minor proportion of aliphatic or cycloaliphatic dicarboxylic acids, and from various polyols such as ethylene glycol, neopentyl glycol, 1,6-hexanediol, trimethylolpropane, and the like.
• polyesters based on aromatic dicarboxylic acids when they are used with an appropriate cross-linking agent, provide thermosetting compositions giving paint and varnish coatings possessing good properties, both as regards their appearance and as regards their mechanical properties such as impact resistance, flexibility, etc.
• polyesters and the powders derived from them often are used because of their remarkable weatherability characteristics.
• These polyesters mostly are derived from isophthalic acid, being the most important acid constituent among others.
• the coatings obtained from these powders though proving outstanding weatherability, do not have any flexibility at all.
• EP 649890 discloses powder coating compositions comprising a ⁇ -hydroxyalkylamide cross-linking agent and an acid functional polyester having an acid number ranging from 15 through 70 mg KOH/g which is substantially based on dicarboxylic acid units containing 80 to 100% mole of isophthalic acid, on glycols containing at least 50% mole of branched aliphatic glycols with at least 4 carbon atoms, at most 50% mole of a linear aliphatic diol with less than 4 carbon atoms and/or cycloaliphatic diols, 0 to 10% mole of a linear aliphatic diol with at least 4 carbon atoms and on monomers having a functionality of at least three, in an amount of 2 to 8% mole based on the total amount of dicarboxylic acids and glycols.
• polyester resins As appears from the examples, all polyester resins, as illustrated, have acid numbers of from 48 to 52 mg KOH/g and contain a monomer having a functionality of three. Only a very few powders of this invention give good flow on melting, which results in coatings having a bad surface appearance. No powders, having as binder constituent a polyester resin with an acid number lower than 48 mg KOH/g, are illustrated.
• EP 389926 describes flexible outdoor durable powder paints derived from isophthalic acid rich polyesters.
• thermosetting powder coating compositions derived from carboxyl functional isophthalic acid rich amorphous polyesters is the use of semi-crystalline acid functional polyesters as co-reactable part of the carboxylic acid amorphous resin in a binder along with a polyepoxy compound or a ⁇ -hydroxyalkylamides, such as disclosed in e.g. WO 91/14745.
• a careful selection of the proper combination of amorphous and semi-crystalline resins, respectively, enables for flexible and weatherable powder coating compositions derived from carboxyl functional isophthalic acid rich polyesters, as far as particular process conditions for mixing, extrusion and grinding are exercised and appropriate storage conditions of the powder thus obtained, are considered.
• the solution presented in this invention to mix a semi-crystalline acid functional polyesters with a carboxyl functional amorphous polyester represents a technical complication.
• polyester A) is an isophthalic acid rich polyester, containing linear chain aliphatic (poly)ether diols and/or linear chain diols
• polyester B) is a terephthalic acid rich polyester, along with a curing agent having functional groups reactable with the polyesters' A) and B) carboxylic end groups
• the combination of paint performances as obtained from the particular binder composition according to the present invention is not obtained from powder coating compositions derived from a binder in which the mixture of both separated resins A) and B) is replaced by a single resin having a monomer composition identical to the one of both resins A) and B) together. Also, it will appear that if the linear chain aliphatic (poly)ether diols and/or linear chain diols is omitted from polyester A), the good combination of said paint performances obtained according to the invention cannot be obtained.
• thermosetting compositions for coatings wherein the binder comprises a blend of two carboxyl group containing polyesters and one or more cross-linkers having functional groups reactable with both the polyesters' carboxylic groups, characterised in that said polyester blend comprises:
• the acid constituent of the isophthalic acid rich polyester A) according to the present invention is for 85 to 100% mole composed of isophthalic acid and for 0 to 15% mole of another polyacid constituent selected from one or more aliphatic, cycloaliphatic or aromatic polyacids, such as fumaric acid, maleic acid, phthalic acid, terephthalic acid, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, succinic acid, adipic acid, glutaric acid, pimelic acid, suberic acid, azealic acid, sebacic acid, 1,12-dodecanedioic acid, trimellitic acid or pyromellitic acid, etc., or the corresponding anhydrides.
• another polyacid constituent selected from one or more aliphatic, cycloaliphatic or aromatic polyacids, such as fumaric acid, male
• the glycol constituent of the isophthalic acid rich polyester A) is for 5 to 60% mole composed of a linear chain aliphatic (poly)ether diol such as diethylene glycol, dipropylene glycol, triethylene glycol and tripropylene glycol, used in a mixture or alone and/or linear chain aliphatic diol, preferably a C 2 - C 16 -diol such as ethyleneglycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-dodecanediol, 1,14-tetradecandiol, 1,16-hexadecandiol, used in a mixture or alone.
• the glycol constituent of this polyester also comprises 40 to 95% mole of neopentyl glycol and for 0 to 30% mole and preferably for 0 to 20% mole of another polyol constituent selected from one or more aliphatic or cycloaliphatic polyol such as propylene glycol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, hydrogenated Bisphenol A, 2-methyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, neopentyl glycol hydroxypivalate, trimethylolpropane, ditrimethylolpropane, pentaerythrytol, etc.
• another polyol constituent selected from one or more aliphatic or cycloaliphatic polyol such as propylene glycol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, hydrogenated Bisphenol A
• the polyester A) according to the present invention is composed of polycarboxylic acid units containing from 85 to 100% mole of isophthalic acid, from 0 to 15% mole of adipic acid and/or 1,4-cyclohexanedicarboxylic acid, and of polyol constituents containing from 5 to 60% mole of linear chain aliphatic (poly)ether diol preferably diethylene glycol, and /or linear chain aliphatic diol, preferably ethylene glycol or/and 1,6-hexanediol, from 40 to 95% mole of neopentyl glycol and from 0 to 30% mole of trimethylolpropane or pentaerythrytol. More preferably, this polyester A) does not contain trimethylolpropane nor pentaerythrytol. This preferred polyester A) is used in an amount of 35 to 65% weight relative to the total amount of polyesters A) and B).
• the acid constituent of the terephthalic acid rich polyester B) according to the present invention is for 70 to 100% mole composed of terephthalic acid and for 0 to 30% mole of another polyacid constituent selected from one or more aliphatic, cycloaliphatic or aromatic polyacids, such as fumaric acid, maleic acid, phthalic acid, isophthalic acid, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, succinic acid, adipic acid, glutaric acid, pimelic acid, suberic acid, azealic acid, sebacic acid, 1,12-dodecanedioic acid, trimellitic acid or pyromellitic acid, etc., or the corresponding anhydrides.
• another polyacid constituent selected from one or more aliphatic, cycloaliphatic or aromatic polyacids, such as fumaric acid,
• the glycol constituent of the terephthalic acid rich polyester B) according to the present invention is for 50 to 100% mole composed of neopentyl glycol and for 0 to 50% mole of another polyol constituent selected from one or more aliphatic or cycloaliphatic polyol such as ethylene glycol, diethylene glycol, propylene glycol, 1,6-hexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, hydrogenated Bisphenol A, 2-methyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, neopentyl glycol hydroxypivalate, trimethylolpropane, ditrimethylolpropane, pentaerythrytol, etc.
• another polyol constituent selected from one or more aliphatic or cycloaliphatic polyol such as ethylene glycol, diethylene glycol, propy
• the polyester B) according to the present invention is composed of polycarboxylic acid units containing from 70 to 100% mole of terephthalic acid, from 0 to 30% mole of isophthalic acid and/or adipic acid, and of polyol constituents containing from 50 to 100% mole of neopentyl glycol and from 0 to 50% mole of 2-butyl-2-ethyl-1, 3-propanediol, neopentyl glycol hydroxypivalate, trimethylolpropane or pentaerythrytol. More preferably, this polyester B) does not contain trimethylolpropane nor pentaerythrytol. This preferred polyester B) is used in amount of 65 to 35% weight relative to the total amount of polyesters A) and B).
• the carboxylic acid group containing amorphous polyesters are usually prepared using conventional esterification techniques well known in the art.
• the polyesters may be prepared according to a procedure consisting of one or more reaction steps.
• a conventional reactor equipped with a stirrer, an inert gas (nitrogen) inlet, a thermocouple, a distillation column connected to a water-cooled condenser, a water separator and a vacuum connection tube is generally used.
• the esterification conditions used to prepare the polyesters are generally conventional, namely a standard esterification catalyst, such as dibutyltin oxide, dibutyltin dilaurate, n-butyltin trioctoate, sulphuric acid or a sulphonic acid, tetraisopropyl titanate or tetra-n-butyl titanate can be used in an amount from 0.05 to 1.50% by weight of the reactants and optionally, colour stabilisers, for example, phenolic antioxidants such as Irganox 1010 (Ciba) or phosphonite- and phosphite-type stabilisers such as tributylphosphite, can be added in an amount from 0 to 1% by weight of the reactants.
• a standard esterification catalyst such as dibutyltin oxide, dibutyltin dilaurate, n-butyltin trioctoate, sulphuric acid or a sulph
• Polyesterification is generally carried out at a temperature which is gradually increased from 130°C to about 190 to 250°C, first under normal pressure, then, when necessary, under reduced pressure at the end of each process step, while maintaining these operating conditions until a polyester is obtained, which has the desired hydroxyl and/or acid number.
• the degree of esterification is followed by determining the amount of water formed in the course of the reaction and the properties of the obtained polyester, for example the hydroxyl number, the acid number, the molecular weight or the viscosity.
• the carboxyl functional polyesters A) and B) of the present invention both are preferably characterised by:
• the carboxyl group containing polyester A) and B), as described above, are part of a binder system along with one or more crosslinkers, preferably chosen from epoxy group and/or ⁇ -hydroxyalkylamide group containing cross-linkers, in the preparation of powder coating compositions for use as paint or clear lacquer.
• the ratio of the isophthalic acid rich polyester A) to the terephthalic acid rich polyester B) varies from 80/20 to 20/80 dependent on whether more outdoor resistance or more flexibility is aimed for.
• the polyesters can be blended in the melt by adding polyester A) to B) or B) to A) and mixing them in the stirred reactor used for their preparation, or by using a static mixer or by extrusion or by any other means being used for blending resins.
• the resins A) and B) also can be added as separate resins to the premix along with the cross-linker(s) and, optionally, the other constituents needed for the preparation of a powder coating formulation.
• the polyepoxy compound, usuable as cross-linker in the binder composition of the present invention generally is solid at room temperature, and contains at least two epoxy groups per molecule such as for example, triglycidyl isocyanurate (TGIC) like the one marketed under the tradename of Araldite PT810 or the mixture of diglycidyl terephthalate and triglycidyl trimellitate, like the one marketed under the tradename of Araldite PT910 or PT912 or acrylic copolymers containing glycidyl groups obtained from glycidyl methacrylate and/or glycidyl acrylate and a (meth)acrylic monomer and, optionally, an ethylenically mono-unsaturated monomer different from glycidyl (meth) acrylate or from the (meth)acrylic monomer.
• TGIC triglycidyl isocyanurate
• Araldite PT810 the mixture of
• ⁇ -hydroxyalkylamide containing compound usuable as cross-linker in the binder composition of the present invention, generally answers the general structure as represented in Formula I. Wherein:
• compositions within the scope of the present invention which comprise 100 to 50% weight of the binder can also include from 0% to 50% weight of various additives.
• additives comprise cross linking catalysts such as amines (e.g. 2-phenylimidazoline), phosphines (e.g. triphenylphosphine), ammonium salts (e.g. tetrabutylammonium bromide or tetrapropylammonium chloride), phosphonium salts (e.g.
• UV-light absorbers such as Tinuvin 900 (Ciba), hindered amine light stabilisers represented by Tinuvin 144 (Ciba), other stabilising agents such as Tinuvin 312 and 1130 (Ciba), antioxidants such as Irganox 1010 (Ciba) and stabilisers from the phosphonite or phosphite type can be added.
• pigments and pigments can be utilised in the composition of this invention.
• useful pigments and dyes are: metallic oxides such as titaniumdioxide, ironoxide, zincoxide and the like, metal hydroxides, metal powders, sulphides, sulphates, carbonates, silicates such as ammoniumsilicate, carbon black, talc, china clay, barytes, iron blues, leadblues, organic reds, organic maroons and the like.
• compositions according to the invention permit to prepare high gloss coatings with both improved outdoor durability and improved flexibility.
• the components of the composition according to the invention may be mixed by dry blending in a mixer or blender (e.g. drum mixer).
• the premix is then homogenised at temperatures ranging from 70 to 150°C in a single screw extruder such as the BUSS-Ko-Kneter or a double screw extruder such as the PRISM or APV.
• the extrudate when cooled down, is grounded to a powder with a particle size ranging from 10 to 150 ⁇ m.
• the powdered composition may be deposited on the substrate by use of a powder gun such as an electrostatic CORONA gun or TRIBO gun.
• well-known methods of powder deposition such as the fluidised bed technique can be used. After deposition the powder is heated to a temperature between 140 and 250°C, causing the particles to flow and fuse together to form a smooth, uniform, continuous, uncratered coating on the substrate surface.
• a mixture of 360.597 parts of neopentyl glycol and 63.635 parts of 1,6-hexanediol are placed in a conventional four neck round bottom flask equipped with a stirrer, a distillation column connected to a water cooled condenser, an inlet for nitrogen and a thermometer attached to a thermoregulator.
• the flask contents are heated, while stirring under nitrogen, to a temperature of circa 130°C at which point 708.559 parts of isophthalic acid and 2.472 parts of n-butyltin trioctoate are added. The heating is continued gradually to a temperature of 230°C. Water is distilled from the reactor from 180°C on.
• Example 1 A mixture of 337.948 parts of neopentyl glycol and 91.892 parts of diethylene glycol are placed in a reactor as for Example 1. At a temperature of 130°C, 712.333 parts of isophthalic acid and 2.473 parts of n-butyltin trioctoate are added. The reaction is continued at 230°C as in Example 1. When transparent, 0.990 tributylphosphite parts are added and vacuum is applied until following characteristics are obtained: AN 29.4 mg KOH/g OHN 1.8 mg KOH/g Brookfield 175°C (cone/plate) 4820 mPa.s Tg (DSC, 20°/min) 52°C
• polyester resin is cooled down to 180°C and 2.475 parts of ethyltriphenylphosponium bromide are added. Half an hour after the addition the reactor is emptied.
• a mixture of 418.714 parts of neopentyl glycol are placed in a reactor as for Example 1.
• a temperature of 130°C 530.841 parts of terephthalic acid, 33.532 parts of adipic acid, 33.355 parts of isophthalic acid and 1.500 parts of n-butyltin trioctoate are added and the mixture is heated to 230°C.
• the reaction is continued at 230°C under atmospheric pressure until about 95% of the theoretical amount of water is distilled and a transparent hydroxyl functionalised prepolymer with following characteristics is obtained: AN 9 mg KOH/g OHN 87 mg KOH/g
• Example 2 A mixture of 426.546 parts of neopentyl glycol are placed in a reactor as for Example 1. At a temperature of 130°C 611.986 parts of terephthalic acid and 2.264 parts of n-butyltin trioctoate are added. The reaction is continued as in Example 3 until following characteristics is obtained: AN 7 mg KOH/g OHN 55 mg KOH/g
• Example 3 To the first step prepolymer standing at 200°C, 56.339 parts of isophthalic acid and 49.562 parts of adipic acid are added. Thereupon, the reaction is continued as for Example 3. When the resin is transparent, 0.906 parts of tributylphosphite are added and vacuum applied until following characteristics are obtained: AN 31.9 mg KOH/g OHN 2.3 mg KOH/g Brookfield 200° C (cone/plate) 3550 mPa.s Tg (DSC, 20°/min) 57°C
• polyester resin is cooled down to 180°C and 2.475 parts of ethyltriphenylphosponium bromide are added. Half an hour after the addition the reactor is emptied.
• Example 2 A mixture of 381.236 parts of neopentyl glycol and 42.359 parts of diethylene glycol are placed in a reactor as for Example 1. At a temperature of 130°C 304.678 parts of terephthalic acid, 273.847 parts of isophthalic acid, 25.994 parts of adipic acid and 2.241 parts of n-butyltin trioctoate are added. The reaction is continued as in Example 3 until following characteristics are obtained: AN 12 mg KOH/g OHN 61 mg KOH/g
• Example 3 To the first step prepolymer standing at 230°C, 115.057 parts of isophthalic acid are added. Thereupon, the reaction is continued as in Example 3 . When the resin is transparent, 0.896 parts of tributylphosphite are added and a vacuum is applied until following characteristics are obtained: AN 33.4 mg KOH/g OHN 1.4 mg KOH/g Brookfield 200°C (cone/plate) 1800 mPa.s Tg (DSC, 20°/min) 55°C
• polyester resin is cooled down to 180°C. and 2.500 parts of ethyltriphenylphosponium bromide are added. Half an hour after the addition the reactor is emptied.
• polyesters as illustrated above are then formulated to a powder according to the formulation as mentioned below.
• Formulation C Brown paint formulation Binder 78.33 Bayferrox 130 4.44 Bayferrox 3950 13.80 Carbon Black FW2 1.09 Resiflow PV5 0.99 Benzoin 0.35
• the powders are prepared first by dry blending of the different components and then by homogenisation in the melt using a PRISM 16 mm L/D 15/1 twin screw extruder at an extrusion temperature of 85°C.
• the homogenised mix is then cooled and grinded in an Alpine.
• the powder is sieved to obtain a particle size between 10 and 110 ⁇ m.
• the powder thus obtained is deposited on cold rolled steel with a thickness of 0.8 mm, by electrostatic deposition using the GEMA - Volstatic PCG 1 spraygun. At a film thickness of about 80 ⁇ m the panels are transferred to an air-ventilated oven, where curing proceeds for 15 minutes at a temperature of 200°C.
• the paint characteristics for the finished coatings obtained from the polyesters in the mixture of the present invention (Ex. 1 to 4) as well as from the two polyesters of example 5 and 6, illustrated by way of comparison, are given in table 1.
• powder coatings derived from isophthalic acid based polyesters (Ex. 8 & Ex.12) have very good UV-B resistance, yet prove a lack of flexibility.
• powder coatings derived from terephthalic acid rich polyesters have good flexibility, yet prove a lack of UV-B resistance (Ex 9. & Ex. 13).
• the powders of Ex. 10 and Ex. 14, according to the present invention and based on a mixture of an isophthalic acid rich polyester and a terephthalic acid rich polyester, prove paint properties tending towards the best of each constituent, i.e. good flexibility of the terephthalic acid rich constituent and good UV-B resistance of isophthalic acid rich constituent.
• neopentyl glycol 418.443 parts are placed in a conventional four neck round bottom flask equipped with a stirrer, a distillation column connected to a water cooled condenser, an inlet for nitrogen and a thermometer attached to a thermoregulator.
• the flask contents are heated, while stirring under nitrogen, to a temperature of circa 130°C at which point 718.897 parts of isophthalic acid and 2.481 parts of n-butyltin trioctoate are added. The heating is continued gradually to a temperature of 230°C. Water is distilled from the reactor from 180°C on.
• the resins of example 16 and 17 are formulated into a brown paint formulation according to example 7. After application and curing for 15 minutes at 200°C, paint performances, as reproduced in the table below, are obtained.. In the same way a mixture composed of 40 parts of the polyester of example 16 and 60 parts of the polyester of example 17 are formulated into the brown paint formulation of example 20. Paint performances are given in table 2.

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Cited By (11)

Citations (5)

• 2004
  • 2004-01-09 EP EP04000371A patent/EP1553148A1/de not_active Withdrawn

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